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reservator.ts
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reservator.ts
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import { AlreadyReservedError, NoReservationError } from "./errors.ts";
/**
* A class representing a Reservator which can reserve and resolve a value with a given key.
*
* @template K The type of the key.
* @template V The type of the value.
*/
export class Reservator<K, V> {
#map: Map<K, { resolve: (v: V) => void; reject: (v: unknown) => void }>;
/** Constructs a new Reservator instance. */
constructor() {
this.#map = new Map();
}
/** Returns the number of reservations. */
get size(): number {
return this.#map.size;
}
/** Removes all reservations. */
clear(): void {
this.#map.clear();
}
/**
* Reserves a value with the given key.
*
* @param key The key to reserve the value with.
* @returns A Promise that resolves with the reserved value.
* @throws {AlreadyReservedError} If a reservation with the given key already exists.
*/
reserve(key: K): Promise<V> {
if (this.#map.has(key)) {
throw new AlreadyReservedError(
`Reservation with key ${key} already exists`,
key,
);
}
const { promise, resolve, reject } = Promise.withResolvers<V>();
this.#map.set(key, { resolve, reject });
return new Promise((resolve, reject) => {
promise.then(resolve, reject);
});
}
/**
* Resolves the reservation with the given key to the given value.
*
* @param key The key of theservation to resolve.
* @param value The value to resolve the reservation with.
* @throws {NoReservationError} If a reservation with the given key does not exist.
*/
resolve(key: K, value: V): void {
const v = this.#map.get(key);
if (!v) {
throw new NoReservationError(
`Reservation with key ${key} does not exist`,
key,
);
}
this.#map.delete(key);
v.resolve(value);
}
/**
* Rejects the reservation with the given key with the given reason.
*
* @param key The key of the reservation to reject.
* @param reason The reason to reject the reservation with.
* @throws {NoReservationError} If a reservation with the given key does not exist.
*/
reject(key: K, reason?: unknown): void {
const v = this.#map.get(key);
if (!v) {
throw new NoReservationError(
`Reservation with key ${key} does not exist`,
key,
);
}
this.#map.delete(key);
v.reject(reason);
}
}